Resilient radiopaque electrophysiology electrodes and probes including the same

ABSTRACT

A coil electrode for use in an electrophysiology probe includes a first material having a relatively high radiopacity and a second material having a relatively high resiliency. This combination provides the necessary levels of durability, resiliency and radiopacity. An electrophysiological probe includes a support structure, at least one first electrode defining a first radiopacity supported on the support structure and at least one second electrode defining a second radiopacity supported on the support structure, the second radiopacity being greater than the first radiopacity. When viewed under a fluoroscope, the pattern of electrodes of varying radiopacities allows the physician to distinguish between individual electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of co-pending U.S.application Ser. No. 09/055,175, filed Apr. 3, 1998, which is itself acontinuation-in-part of U.S. application Ser. No. 08/558,131, filed Nov.13, 1995, now U.S. Pat. No. 5,797,905, which is itself acontinuation-in-part of both U.S. application Ser. No. 08/287,192, filedAug. 8, 1994, now abandoned, and U.S. application Ser. No. 08/439,824,filed May 12, 1995, now U.S. Pat. No. 5,810,802, all of which areincorporated herein by reference.

BACKGROUND OF THE INVENTIONS

[0002] 1. Field of Inventions

[0003] The present inventions relate generally to electrophysiologyprobes such as catheters and surgical probes and, more particularly, toelectrodes for use with electrophysiology probes.

[0004] 2. Description of the Related Art

[0005] Catheters, surgical probes and related electrophysiologicaldevices (together referred to herein as “electrophysiological probes” or“probes”) are used today in diagnostic and therapeutic medicalprocedures that require surgical or minimally invasive access totargeted tissue areas within interior regions of the body. The probesinclude support bodies that typically carry an array of linearly spacedelectrodes at the distal end thereof. Probe power control systems thatallow physicians to individually control the power applied to theelectrodes in such multiple electrode probes are also available. Oneexample of such a system is disclosed in U.S. Pat. No. 5,545,193.

[0006] Precise positioning of the electrodes is of paramount importancein all probe-based procedures. However, the need for careful and precisepositioning of the electrodes is especially critical during certainprocedures concerning the heart. These procedures, calledelectrophysiological therapy, are becoming more widespread for treatingcardiac rhythm disturbances. Cardiac tissue coagulation (sometimesreferred to as “ablation”), where therapeutic lesions are formed incardiac tissue, is one procedure in which the ability to preciselyposition the electrodes is especially important. During catheter-basedprocedures, a physician steers the catheter through a main vein orartery into the region of the heart that is to be treated. In surgicalprobe-based procedures, the distal portion of the probe is insertedthrough the patient's chest and directly into the heart. The physicianmust then precisely place the linear array of electrodes near thecardiac tissue that is to be coagulated. Fluoroscopic imaging in oftenused to identify anatomic landmarks within the heart and to position theelectrodes relative to the targeted tissue region. Once the electrodesare properly positioned, the physician directs energy from theelectrodes to the tissue to form a lesion.

[0007] Rigid ring-shaped electrodes were originally used inelectrophysiological probes. In recent years, coil electrodes have beenintroduced in order to increase the flexibility of the distal portion ofthe probes, thereby enabling the physician to more precisely control theposition and shape of the distal portion of the probe and to achievesuperior tissue contact. The metals used to manufacture conventionalcoil electrodes have been heretofore selected according to certainmechanical properties, the primarily property being resiliency. Arelatively high level of resiliency is required during the variousmanufacturing processes, such as coil winding and the mounting of coilsonto a probe, because relatively resilient material returns to itsoriginal shape after being manipulated during manufacturing, as comparedto softer, less resilient materials such as platinum or gold which canbe permanently deformed during manufacturing. Relatively resilientmaterials are also more durable than softer, less resilient materials.Another desirable mechanical property is stiffness. Accordingly, coilelectrodes have been formed from relatively resilient and stiffmaterials and, more specifically, from stainless steel.

[0008] The radiopacity of stainless steel is, however, relatively low.Thus, while otherwise superior to coil electrodes formed from lessresilient materials such as platinum or gold, stainless steel coilelectrodes are difficult to visualize using fluoroscopic imagingtechniques. The low visibility of conventional stainless steel coilelectrodes makes it difficult to properly position the distal portion ofthe probe. It is also difficult to differentiate between individual coilelectrodes which, in turn, makes individual control of the electrodesdifficult even when the distal portion of the probe is properlypositioned. The difficulties associated with electrode differentiationare further compounded when the probe includes a relatively large numberof electrodes.

[0009] One proposed solution to this problem has been to includeradiopaque markers on probes in addition to the electrodes. Theinventors herein have determined that this proposed solution is lessthan optimal because the electrodes must be closely spaced in order toinsure reliable creation of contiguous lesions between adjacentelectrodes. The close spacing precludes the placement of radiopaquemarkers between the electrodes.

SUMMARY OF THE INVENTION

[0010] The inventors herein have determined that a need exists for anelectrophysiology probe having coil electrodes that are both resilientand radiopaque. Accordingly, one object of the present invention is toprovide an electrophysiology probe having one or more coil electrodesthat have relatively high levels of resiliency and radiopacity. Anotherobject of the present invention is to provide an electrophysiologicalprobe having an electrode arrangement that facilitates electrodeidentification.

[0011] In order to accomplish some of these and other objectives, a coilelectrode for use in an electrophysiology probe in accordance with apresent invention is formed from a first material having a relativelyhigh radiopacity and a second material having a relatively highresiliency. In one embodiment, the electrode includes a stainless steelcladding over a relatively soft 90/10 platinum/iridium core. Thestainless steel cladding provides the necessary levels of durability andresiliency for coil winding and assembly, while the platinum/iridiumcore provides the necessary level of radiopacity.

[0012] In order to accomplish some of these and other objectives, anelectrophysiological probe in accordance with a preferred embodiment ofa present invention includes a support structure, at least one firstelectrode defining a first radiopacity supported on the supportstructure and at least one second electrode defining a secondradiopacity supported on the support structure, the second radiopacitybeing greater than the first radiopacity. In one embodiment, the probeincludes a plurality of first and second electrodes arranged in apredetermined pattern. When viewed under a fluoroscope, the pattern ofobjects having relatively high and low radiopacities allows thephysician to distinguish between individual electrodes.

[0013] The above described and many other features and attendantadvantages of the present inventions will become apparent as theinventions become better understood by reference to the followingdetailed description when considered in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Detailed description of preferred embodiments of the inventionswill be made with reference to the accompanying drawings.

[0015]FIG. 1 is a plan view of an electrophysiology probe in accordancewith a preferred embodiment of a present invention.

[0016]FIG. 2 is a cutaway view of the electrophysiology probe handleillustrated in FIG. 1.

[0017]FIG. 3 is an exploded view of certain components of the distalportion of the electrophysiology probe illustrated in FIG. 1.

[0018]FIG. 4 is a plan view of an electrophysiology probe in accordancewith another preferred embodiment of a present invention.

[0019]FIG. 5 is a section view of the proximal portion of theelectrophysiological probe shaft illustrated in FIG. 4 taken along line5-5 in FIG. 4.

[0020]FIG. 6 is a section view of the distal portion of theelectrophysiological probe illustrated in FIG. 4 taken along line 6-6 inFIG. 4.

[0021]FIG. 7 is a section view of a preferred electrophysiological probedistal portion.

[0022]FIG. 8a is a side, partial section view of an electrode andsupport structure in accordance with a preferred embodiment of a presentinvention.

[0023]FIG. 8b is a side, partial section view of an electrode andsupport structure in accordance with another preferred embodiment of apresent invention.

[0024]FIG. 9a is a side, partial section view of an electrode andsupport structure in accordance with still another preferred embodimentof a present invention.

[0025]FIG. 9b is a side, partial section view of an electrode andsupport structure in accordance with yet another preferred embodiment ofa present invention.

[0026]FIG. 10 is a side view of an electrode in accordance with anotherpreferred embodiment of a present invention.

[0027]FIG. 11 is a partial side view of the electrode illustrated inFIG. 10 mounted on a support structure with a temperature sensor.

[0028]FIG. 12 is a section view of the electrode illustrated in FIG. 10.

[0029]FIG. 13 is a partial plan view of an electrophysiological probe inaccordance with a preferred embodiment of a present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The following is a detailed description of the best presentlyknown modes of carrying out the inventions. This description is not tobe taken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the inventions.

[0031] The detailed description of the preferred embodiments isorganized as follows:

[0032] I. Introduction

[0033] II. Electrophysiological Probe Structures

[0034] III. Electrophysiological Probe Electrodes

[0035] IV. Electrode Identification

[0036] The section titles and overall organization of the presentdetailed description are for the purpose of convenience only and are notintended to limit the present inventions.

[0037] I. Introduction

[0038] The present inventions are directed generally toelectrophysiological probes and electrophysiological probe electrodesthat may be used within body lumens, chambers or cavities for diagnosticor therapeutic purposes without complex invasive surgical procedures.The inventions herein have particular application in the diagnosis andtreatment of arrhythmia conditions within the heart because they canfacilitate intimate tissue contact with target substrates associatedwith various arrhythmias, namely atrial fibrillation, atrial flutter,and ventricular tachycardia. Nevertheless, it should be appreciated thatthe electrophysiological probes and electrodes are applicable for use intherapies involving other types of soft tissue. For example, variousaspects of the present inventions have applications in proceduresconcerning other regions of the body such as the prostate, liver, brain,gall bladder, uterus and other solid organs.

[0039] II. Electrophysiological Probe Structures

[0040] As illustrated for example in FIGS. 1-3, an electrophysiologicalprobe in accordance with a preferred embodiment of a present inventionmay be in the form of a catheter 10 including a catheter body 12 and ahandle 14. The distal portion 16 of the catheter body 12 supports aplurality of coil electrodes 18. The catheter body 12 preferablyconsists of two tubular parts, or members. The proximal member 20 isrelatively long and is attached to the handle 14, while the distalmember 22, which is relatively short, carries the coil electrodes 18.The proximal member 20 is typically formed from material, such asbraided PEBAX® (with a hardness durometer of 55 D), which has bettertorque transmission properties than the distal member 22, which istypically formed from a softer, more flexible material such as PEBAX®(with a hardness durometer of 35 D), that is better for steering. Aguide coil 24 is disposed within the central lumen of the proximalmember 20. Additional details concerning such a catheter body aredisclosed in U.S. application Ser. No. 09/150,833, filed Sep. 10, 1998,entitled “Catheter Having Improved Torque Transmission Capabilities andMethod of Making the Same,” which is incorporated herein by reference.

[0041] The exemplary catheter 10 also includes a steering mechanism 26that may be used to deflect the distal portion 16 of the catheter body12 in the manner illustrated in FIG. 1. In the preferred embodiment, thesteering mechanism 26 consists of a rotatable cam wheel 28 and steeringlever 30 arrangement that is mounted on the handle 14 and a pair ofsteering wires 32 and 34 that are secured to opposite sides of asteering spring 36 (sometimes referred to as a “center support”). Oneend of the steering spring is secured to the distal end of the guidecoil 24 and the other end is secured to a catheter tip 37. Additionaldetails concerning this and other steering arrangements are disclosed inU.S. Pat. No. 5,254,088, which is incorporated herein by reference, aswell as in the aforementioned U.S. application Ser. No. 09/150,833.

[0042] The exemplary catheter 10 may be used in conjunction with aconventional tissue mapping and coagulation energy supply apparatuswherein power from an electromagnetic radio frequency (about 10 kHz toabout 3 GHz) generator is supplied to the electrodes and controlledbased upon temperature. To that end, and as discussed in Section IIIbelow, a plurality of temperature sensors (such as thermocouples orthermistors) may be located on, under, abutting the longitudinal endedges of, or in between, the electrodes 18. A plurality of lead (or“signal”) wires are electrically connected to the electrodes 18 andtemperature sensors, extend through the catheter body 12 into the handle14, where they are electrically coupled to an external connector 38(note, for example, wire 73 in FIGS. 9a and 9 b). The connector 38connects the electrodes 18 and temperature sensors to the mapping andenergy supply apparatus. The apparatus should be operable in bothbi-polar and uni-polar modes: When operated in a uni-polar mode, anexternal patch electrode (not shown) constitutes the radio frequencyenergy return line.

[0043] As shown by way of example in FIGS. 4-7, an electrophysiologicalprobe in accordance with another preferred embodiment of a presentinvention may be in the form of a surgical probe 40 that includes arelatively short, relatively stiff shaft 42, a handle 44 and a distalsection 46. The distal section 46 supports a plurality of coilelectrodes 48 and a tip electrode 50. The shaft 42 may be from about 4inches to 18 inches in length and is preferably about 6 to 8 inches. Thedistal section 46 may be from about 1 inch to 10 inches in length and ispreferably about 4 to 6 inches. This embodiment is particularly usefulbecause it can be easily inserted into the patient through anintroducing port such as a trocar.

[0044] The exemplary shaft 42 illustrated in FIGS. 4 and 5 consists of ahypo-tube 52, which is relatively stiff, and an outer polymer tubing 54over the hypo-tube. A “relatively stiff” shaft (or other structuralelement) is either rigid, malleable, or somewhat flexible. A rigid shaftcannot be bent. A malleable shaft is a shaft that can be readily bent bythe physician to a desired shape, without springing back when released,so that it will remain in that shape during the surgical procedure.Thus, the stiffness of a malleable shaft must be low enough to allow theshaft to be bent, but high enough to resist bending when the forcesassociated with a surgical procedure are applied to the shaft. Asomewhat flexible shaft will bend and spring back when released.However, the force required to bend the shaft must be substantial. Amalleable or somewhat flexible shaft will preferably have a bendingmodulus of between approximately 3 lb.-in.² and approximately 50lb.-in.². Rigid and somewhat flexible shafts are preferably formed fromstainless steel, while malleable shafts are formed from annealedstainless steel.

[0045] The exemplary surgical probe 40 illustrated in FIGS. 4-7 is alsointended to be used in conjunction with a conventional tissue mappingand coagulation energy supply apparatus. Here too, a plurality oftemperature sensing elements may be located on, under, abutting thelongitudinal end edges of, or in between, the electrodes. Additionally,a reference temperature sensor 56 may be provided in the handle 44 sothat room temperature will be used as the reference. The handle 44 alsoincludes a PC board 58 for connecting the electrodes and temperaturesensors to the power source. The supply of power to the electrodes maybe turned on and off with a foot switch. Alternatively, the handle 44may be provided with a manually operable global on-off switch that canselectively enable and disable the supply of energy to all of theelectrodes. The handle 44 may also include a plurality of individualon-off switches for each electrode.

[0046] The distal section 46 of the exemplary probe 40 can be eithersomewhat flexible, in that it will conform to a surface against which itis pressed and then spring back to its original shape when removed fromthe surface, or malleable. As shown by way of example in FIG. 6, asomewhat flexible distal section 46 may include a spring member 60,which is preferably either a solid flat wire spring (as shown), a roundwire, or a three leaf flat wire Nitinol spring, that is connected to thedistal end of the hypo-tube 52. Other spring members, formed frommaterials such as 17-7 or 455 carpenters steel, may also be used. Aseries of lead wires 62 and 64 connect the electrodes 48 and 50 andtemperature sensors, respectively, to the PC board 58. The spring member60 and lead wires 62 and 64 are enclosed in a flexible body 66,preferably formed from PEBAX® material, polyurethane, or other suitablematerials. The spring member 60 may also be pre-stressed so that thedistal tip is pre-bent. An insulating sleeve 68 may be placed betweenthe spring member 60 and the lead wires 62 and 64. In those instanceswhere a malleable distal section 46 is desired, the spring member 60 maybe replaced by a mandrel 70 made of suitably malleable material such asannealed stainless steel or beryllium copper, as illustrated for examplein FIG. 7.

[0047] Additional information concerning the above-described and othersurgical probes may be found in U.S. application Ser. No. 09/072,872,filed May 5, 1998, entitled “Surgical Method and Apparatus forPositioning a Diagnostic or Therapeutic Element Within the Body,” whichis incorporated herein by reference.

[0048] III. Electrophysiological Probe Electrodes

[0049] As illustrated in FIGS. 8a-12, there are a variety of coilelectrode configurations that may be used in conjunction with theelectrophysiological probes described above as well as otherelectrophysiological probes. Referring first to FIG. 8a, anelectrophysiological probe support structure 72 (such as the catheterdistal section 16 or surgical probe distal section 46) may be used tocarry an array of spaced apart, generally flexible coil electrodes 74 a.In this embodiment, each of the coil electrodes 74 a is relativelytightly wound and is circular in cross-section. Alternatively, and asillustrated for example in FIG. 8b, a tightly wound coil electrode 74 bmay be substantially flat, rectangular in cross-section.

[0050] A flat cross-section is preferred for a number of reasons. With aflat cross section, the tissue contact surface area of the coilelectrode 74 b can be increased along the support structure 72, ascompared to the coil electrode 74 a with a circular cross-section,without increasing the outside diameter of the electrode. This resultsin more compact and easily deployable electrodes. A flat cross-sectionalso permits a more efficient transmission of radio frequency energy.With a flat cross-section, the radio frequency electrical energy istransmitted through a rectangular cross-sectional area that is manytimes that of the cross-section of a round wire of identical thickness.Also, substantially fewer windings are required to construct a coilelectrode with a flat cross-section. As a result, there is a lowerelectrical impedance for a flat cross-section wire.

[0051] Whether circular or rectangular in cross-section, the flexibilityof coil electrodes can be increased by introducing space between thecoil windings. As illustrated for example in FIGS. 9a and 9 b, thewindings in each of the coil electrodes 76 a and 76 b have been spreadapart by a distance D, which is the result of increasing the pitch ofthe individual windings. Here too, the cross-section of the coilelectrodes can be either circular (electrode 76 a) or rectangular(electrode 76 b). Preferably, the distance D between the windings shouldbe at least ⅕ of the width W of the windings. The most preferreddistance D is believed to be about ½ of the width W of the windings.However, the actual spacing will depend upon the desired heating effect.If additive heating effects between adjacent windings are desired toform continuous lesions between the windings, the upper spacing limitbecomes the distance at which the desired additive heating effect isobserved to diminish.

[0052] Temperature sensors, such as thermocouples or thermistors, areprovided in conjunction with electrodes in many electrophysiologicalprobes. As illustrated for example in FIGS. 10 and 11, the longitudinalends of a coil electrode 78 may be configured to accommodate optimalplacement of temperature sensors 80. The coil electrode 78 includes afirst zone 82 with spaced windings, which represents the majority of theelectrode, and second zones 84 at each longitudinal end of the electrodewith closely adjacent windings. In the illustrated embodiment, thespacing D between adjacent windings in the first zone 82 issubstantially uniform. However, the spacing D can also be varied by, forexample, progressively decreasing the spacing from the midpoint of thefirst zone 82 to the second zones 84. Whether uniform or varied, thespacing D should be at least ⅕ of the width W. The closeness of thewindings in the second zones 84 provides a support structure for thetemperature sensors 80 which are preferably mounted at or near thelongitudinal end edges of the coil electrodes 78. It is at the edgeswhere electrical conductivity is discontinuous and the resulting rise incurrent density generates localized regions of increased power densityand, therefore, higher temperatures.

[0053] The temperature sensors may be mounted in a variety of ways. Forexample, as shown in solid lines in FIG. 11, the temperature sensors 80may be threaded up through the windings in the second zones 84 to layupon their exterior surfaces and encapsulated in an epoxy orcyanoacrylate adhesive or PTFE coating 86. Preferably, as shown inphantom lines in FIG. 11, the temperature sensors 80 can be secured tothe inside surface of each of the second zones 84. The sensors 80 mayalso be sandwiched between the inside surface of the second zones 84 andthe support structure 72. A thin strip of electrically insulatingmaterial (not shown) may be applied about the support structure 72immediately next to the second zones 84 to help to minimize the presenceof edge effect currents.

[0054] In accordance with a present invention, the coil electrodesdisclosed herein preferably have a relatively high level of resiliencyas well as a relatively high level of radiopacity. In the preferredembodiment, and as shown by way of example in FIG. 12, the coilelectrode 78 (the construction of which may also be applicable to theother electrodes disclosed herein) is a composite coil electrode formedfrom a first material 88 having a relatively high radiopacity and asecond material 90 having a relatively high resiliency. The firstmaterial 88 may, for example, be relatively soft and significantly lessstiff than the second material 90. Although the preferred configurationis one in which the first material 88 having the relatively highradiopacity is generally interior to the second material 90 having therelatively high resiliency, the relative positioning of the materialsmay be reversed.

[0055] The first and second materials may be combined in a drawn filledtubing arrangement that is subsequently rolled into a flat wire, orthrough other techniques. For example, the first and second materialsmay be combined into a multifilament drawn wire including individualstrands of the first and second materials. Such a wire may be obtainedfrom Cathguide Corp. in Miami, Fla. Another method of combining thefirst and second materials involves placing a heat expanded hypotubeformed from the second material over a hypotube formed from the firstmaterial. Cooling of the second material will cause the hypotube formedtherefrom to shrink fit over the hypotube formed from the firstmaterial, thereby forming a composite hypotube that can be drawn to sizeusing conventional techniques.

[0056] One exemplary method of manufacturing the coil electrode 78 is towind drawn, filled tubing or multifilament wire having the desiredcombination of metals around a mandrel in accordance with conventionalcoil fabrication techniques. In those instances where the coil electrode78 is configured in the manner illustrated in FIG. 10, the windings inthe second zones 84 are connected to one another to prevent unraveling(preferably by laser welding) and the longitudinal ends are cut andground to a 90 degree angle with the longitudinal axis of the coil.Alternatively, the drawn, filled tubing can be wound directly onto thesupport structure 72. Another manufacturing method involves machiningthe aforementioned composite hypotube, or a hypotube made of onematerial (such as stainless steel) into a series of spiral coils,thereby forming the coil electrode. Suitable machining techniquesinclude laser cutting, chemical etching and electrical dischargemachining. When the hypotube is only made of one material, the machinedcoil electrode can then be coated with another material (such as gold)by techniques including electroplating, conductive adhesives and ionvapor assisted deposition.

[0057] In any of these configurations, the result of this compositeconstruction is a durable coil electrode that has the resiliencynecessary for winding and/or assembly processes, the flexibilitynecessary for imparting resiliency to the distal portion of the probe,as well as the radiopacity necessary for fluoroscopic imaging.

[0058] In the exemplary embodiment illustrated in FIG. 12, the coilelectrode 78 includes a stainless steel cladding (second material 90)over a 90/10 platinum/iridium core (first material 88). Alternate firstmaterials 88 include platinum, gold, silver, tantalum and otherradiopaque precious metals. The stainless steel is preferably 304, 303,or 17-7. Alternate second materials 90 include Nitinol and titanium.Preferably, the percent recoverable strain of the second material 90will be at least 2% to provide sufficient resiliency.

[0059] Preferably, the radiopacity of the first material 88 will be atleast two (2) times the radiopacity of the second material 90. By way ofbackground, medical fluoroscopy utilizes a low energy x-ray systemwherein photoelectric absorption, as opposed to Compton scattering orother ways in which x-rays interact with matter, becomes the predominantfactor. As a result, in most surgical and interventional procedures, thedegree of visibility will be dependent on the atomic weight of thematerial. Stainless steel, for example, has an atomic weight 57.50,while 24K gold and 90/10 platinum/iridium have respective atomic weightsof 196.97 and 194.80. Thus, the radiopacity of 24K gold and 90/10platinum/iridium is about 3.4 times that of stainless steel.

[0060] With respect to dimensions, the coil electrodes 78 may be sizedto suit particular applications. For example, a coil electrode for usein a catheter-type electrophysiological probe is preferably betweenabout 6 mm and 18 mm in length and between about 1.6 mm and 3 mm inouter diameter, while the coil electrodes in surgical probe willpreferably be between about 6 mm and 18 mm in length and between about1.6 mm and 3 mm in outer diameter. The thickness of the electrodes willbe preferably between about 0.003 inch and 0.012 inch, with thethickness of the first material 88 having a relatively high radiopacitybeing between about 0.001 inch and 0.005 inch and the thickness of thesecond material 90 having a relatively high resiliency being betweenabout 0.002 inch and 0.008 inch. The thickness ratio of the firstmaterial 88 to the second material 90 is preferably between about 0.3and 3.

[0061] Turning to electrode spacing, the spacing between the electrodesis equal to or less than about 3 times the smaller of the diameters ofthe electrodes, the simultaneous emission of energy by the electrodescreates an elongated continuous lesion pattern in the contacted tissuearea due to the additive effects. Similar effects are obtained when thespacing between the electrodes is equal to or less than about 2 timesthe longest of the lengths of the electrodes.

[0062] To consistently form long, continuous curvilinear lesionpatterns, additional spatial relationships among the electrodes must beobserved. When the length of each electrode is equal to or less thanabout 5 times the diameter of the respective electrode, the curvilinearpath that the probe takes should create a distance across the contactedtissue area that is greater than about 8 times the smaller of thediameters of the electrodes. The simultaneous application of energy willform a continuous elongate lesion pattern that follows the curvedperiphery contacted by the probe, but does not span across the contactedtissue area. The same effect will be obtained when the length of eachelectrode is greater than about 5 times the diameter of the respectiveelectrode, and the curvilinear path that support element takes shouldcreate a radius of curvature that is greater than about 4 times thesmallest the electrode diameters. Of course, the spacing between theelectrodes must be such that additive heating effects are created.

[0063] Taking the above considerations into account, the consistentformation of continuous lesions can be obtained, when using coilelectrodes that are about 12.5 mm in length and about 2.33 mm indiameter, with about 2 to 3 mm electrode spacing.

[0064] As the aforementioned sizes and spacings facilitate theproduction a variety of lesions, including large surface area, deeplesions and continuous long thin lesions, the present probes areespecially useful in treating atrial flutter, atrial fibrillation, othersupraventricular tachycardias, and ventricular tachycardia substrates.These electrode configuration also provides detailed mappingcapabilities.

[0065] IV. ELECTRODE IDENTIFICATION

[0066] As illustrated for example in FIG. 13, an electrophysiologicalprobe 92 in accordance with a preferred embodiment of a presentinvention includes an electrode array 94 that facilitates individualelectrode identification when the probe is viewed with a fluoroscope.Although the exemplary array, as well as variations thereof, can be usedin combination with a wide variety of electrophysiological probes,exemplary probe 92 is a loop catheter having a handle 96, a catheterbody including a distal portion 98, a pull wire 100, and a radiopaquedistal marker 102. Additional information concerning loop catheters maybe found in U.S. Pat. No. 5,910,129, which is incorporated herein byreference.

[0067] The exemplary array 94 includes a plurality of radiopaque coilelectrodes 78 (described in Section III above with reference to FIGS.10-12) and a plurality of electrodes 104 that have lower radiopacity.Here, the electrodes 104 are stainless steel coil electrodes. Theexemplary array 94 includes fourteen (14) electrodes numbered 1-14 withthe radiopaque coil electrodes 78 identified with circles around theirrespective electrode numbers in FIG. 13. The array 94 is divided intotwo sets—the distal set (electrodes 1-7) and the proximal set(electrodes 8-14). The proximal-most and distal-most electrodes in eachset (electrodes 1, 7, 8 and 14) are radiopaque coil electrodes 78.Stainless steel electrodes 104 (electrodes 2, 6, 9 and 13) are locatedproximal to the distal-most electrode and distal to the proximal-mostelectrode in each set. This arrangement facilitates identification ofthe distal-most electrode (electrode 1) and the proximal-most electrode(electrode 14). The center point of the overall array is also easilyidentifiable in that it is the only portion of the array that has twoconsecutive radiopaque electrodes 78. In order to provide additionalresolution, radiopaque electrodes 78 (electrodes 4 and 11) may also beplaced at the mid-points of each set.

[0068] Accordingly, and although other patterns may be used, thejuxtaposition of the more radiopaque coil electrodes 78 with thestainless steel coil electrodes 104 in a predetermined pattern allowsthe physician to easily distinguish between the various electrodes inthe array.

[0069] For certain surgical probe applications, such as surgical probesthat can be used during open heart surgery in addition to less invasiveprocedures, the coils may be color coded for positive visualidentification by the physician. A number of different colors (includingthe color of metal that is not otherwise colored) may be employed in thecoding schemes and various conventional techniques may be used to applya colored coating. For example, a thin layer of gold may be depositedonto the exterior surface of the electrode by ion vapor deposition.Titanium plating, which can be processed into a blue color, can also beused. Another technique involves the use of platinum black which, as isknown in the medical arts, is platinum that is made to look blackthrough the use of surface modification techniques.

[0070] The arrangement (or pattern) of the color coded electrodes may,if desired, correspond to the coding arrangement illustrated in FIG. 13.Color coding may also be used in combination with radiopacity-basedcoding by, for example, making the more radiopaque electrodes one colorand the less radiopaque electrodes another color so that the electrodescan be identified both visually and through fluoroscopy.

[0071] Although the present inventions have been described in terms ofthe preferred embodiments above, numerous modifications and/or additionsto the above-described preferred embodiments would be readily apparentto one skilled in the art. It is intended that the scope of the presentinventions extends to all such modifications and/or additions.

We claim:
 1. An electrophysiology probe, comprising: a supportstructure; and at least one coil electrode supported on the supportstructure, the at least one coil electrode being formed from a firstmaterial having a relatively high radiopacity and a second materialhaving a relatively high resiliency.
 2. An electrophysiology probe asclaimed in claim 1 , wherein the first material comprises platinum. 3.An electrophysiology probe as claimed in claim 1 , wherein the secondmaterial comprises stainless steel.
 4. An electrophysiology probe asclaimed in claim 1 , wherein the first material defines a radiopacitysubstantially equal to at least approximately 2 times the radiopacity ofthe second material.
 5. An electrophysiology probe as claimed in claim 1, wherein the second material defines a percent recoverable strainsubstantially equal to at least approximately 2%.
 6. Anelectrophysiology probe as claimed in claim 1 , wherein the secondmaterial defines the exterior of the electrode.
 7. An electrophysiologyprobe as claimed in claim 1 , wherein the first material defines theexterior of the electrode.
 8. An electrophysiology probe as claimed inclaim 1 , wherein the first material defines a core and the secondmaterial defines a cladding over the core.
 9. An electrophysiology probeas claimed in claim 1 , further comprising: an electrical lead wireconnected to the at least one electrode.
 10. An electrophysiology probe,comprising: a support structure; at least one first electrode defining afirst radiopacity supported on the support structure and at least onesecond electrode defining a second radiopacity supported on the supportstructure, the second radiopacity being greater than the firstradiopacity; and a plurality of electrical lead wires respectivelyconnected to the at least one first electrode and at least one secondelectrode.
 11. An electrophysiology probe as claimed in claim 10 ,wherein the at least one first electrode comprises a first materialhaving a relatively high radiopacity and a second material having arelatively high resiliency.
 12. An electrophysiology probe as claimed inclaim 11 , wherein the at least one second electrode is formed from asingle material having a relatively high resiliency.
 13. Anelectrophysiology probe as claimed in claim 12 , wherein the firstmaterial comprises platinum and the second material comprises stainlesssteel.
 14. An electrophysiology probe as claimed in claim 10 , whereinthe at least one first electrode comprises a plurality of firstelectrodes, the at least one second electrode comprises a plurality ofsecond electrodes, and the first and second electrodes together define aproximal set of electrodes and a distal set of electrodes, each setincluding a proximal-most electrode and a distal-most electrode, and thedistal-most electrode in the proximal set and the proximal-mostelectrode in the distal set being second electrodes.
 15. Anelectrophysiology probe as claimed in claim 14 , wherein theproximal-most electrode in the proximal set and the distal-mostelectrode in the distal set are second electrodes.
 16. Anelectrophysiology probe as claimed in claim 15 , wherein the proximalset includes a plurality of first electrodes between the proximal-mostelectrode and distal-most electrode thereof.
 17. An electrophysiologyprobe as claimed in claim 15 , wherein the proximal set further includesa second electrode between a pair of the first electrodes.
 18. Anelectrophysiology probe as claimed in claim 10 , wherein the at leastone first electrode and at least one second electrode together comprisea linear array of electrodes having no more than two consecutive firstelectrodes.
 19. An electrophysiology probe as claimed in claim 10 ,wherein the at least one second electrode comprises a coil electrode.